1. Field of the Invention
The present invention relates to an image capturing apparatus and a method of setting exposure for Auto Focus (AF) control executed by an image capturing apparatus, and in particular, to an image capturing apparatus that illuminates an object with AF auxiliary light when the object is determined to be dark before an AF operation as well as a method of setting exposure for AF control executed by an image capturing apparatus.
2. Description of the Related Art
Image capturing apparatus such as a digital camera and a mobile telephone or personal digital assistant having image capturing function, uses an image pickup element to convert an optical image of an object into an electric signal for recording. In the digital camera, an image taking lens is generally subjected to AF control according to contrast information on an image obtained from the image pickup element (contrast AF). However, when it gets dark as in the case with nighttime, the contrast of the object lowers. In this case, the contrast AF cannot enable a focus state to be properly determined.
Japanese Patent Application Publication No. 8-160489 discloses a camera in which a camera body comprises a light emitting device that illuminates the object with AF auxiliary light when its gets dark. However, this camera simply emits auxiliary light, and overexposure or underexposure may disadvantageously occur during an AF operation depending on the distance to the object. This hinders the focus from being accurately determined.